When microplates are used to hold samples to be assayed by techniques which are dependent on light emissions from the sample, it is important to avoid light transmission between adjacent samples, i.e., "crosstalk." Such crosstalk is extremely undesirable because it means that the photons detected in any particular sample well might not have originated from the particular sample in that well, and the purpose of the assaying technique is to obtain a unique measurement for each individual sample that is representative of only that sample.
In certain applications, it is desirable to have a transparent wall in the bottom of the sample well. For example, when coincidence measurement is used, it is desirable to have a first photodetector at the top of the well, which is normally open, and a second photodetector at the bottom of the well, which is normally closed. Of course, photons can be detected at the bottom of the well only if the wall of the well is transparent. Even when light measurements are not made at the bottom of the well, if is often desirable to have a transparent well wall to allow microscopic viewing of adherent cells within the well.